Spinal fusion instruments and methods

Abstract

An instrument for harvesting an iliac bone graft comprises an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, and a distal working portion including a pair of longitudinally extending, transversely spaced apart blade retaining slots. A pair of chisel-type blades are adapted for being releasably, lockably housed in the slots. The blades are retained in the slots by set screws, and by overhanging lips which engage the blades when fully inserted in the slots. An instrument for inserting an iliac bone graft into a disc space comprises an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, a distal working portion including an enlarged abutment head on its terminal end, and a slide portion disposed between the gripping portion and the working portion, the abutment head having a distal abutment surface for engaging an iliac bone graft. A retainer member is disposed on the slide portion and is slidable between the abutment head and the gripping portions. The retainer member includes a pair of retaining fingers having proximal ends mounted on the retainer member and free distal ends which extend distally beyond the abutment surface of the abutment head when the retaining member is in its distalmost position. The distal ends of the retaining fingers are spring biased toward one another. The abutment head has stop lugs disposed on side extensions for limiting the travel of the abutment head into a disc space.

I claim: 
     
       1. An instrument for harvesting an iliac bone graft, comprising: an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, and a distal working portion comprising the distal terminal end of said handle and including a pair of longitudinally extending, transversely spaced apart blade retaining slots, said slots being substantially parallel to the longitudinal axis of said handle and to one another and extending in a proximal direction from said distal terminal end of said handle part way along the length of said handle; and   a pair of chisel-type blades adapted for being releasably, lockably housed in said slots said blades each having a main body portion and a shank portion, said shank portions each being adapted for placement in said slots and each having a keyway therein, and wherein said slots each have a longitudinally extending planar base surface and transversely extending, opposed side walls, each of said slots being open in a direction normal to said planar base surfaces at least to the extent of permitting passage of said shank portions into or out of said slots along said normal directions, and said base surfaces each include a transversely extending threaded bore for receiving one of a pair of set screws, said set screws being engageable with said keyways of said blades for locking said blades in said slots.   
     
     
       2. An instrument for harvesting an iliac bone graft, comprising: an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, and a distal working portion including a pair of longitudinally extending, transversely spaced apart blade retaining slots; and   a pair of chisel-type blades adapted for being releasably, lockably housed in said slots, wherein said blades each have a main body portion and a shank portion, said shank portions each being adapted for placement in said slots and each having a keyway therein, and wherein said slots each have a longitudinally extending planar base surface and transversely extending, opposed side walls, and said base surfaces each include a transversely extending threaded bore for receiving one of a pair of set screws, said set screws being engageable with said keyways of said blades for locking said blades in said slots, wherein said keyways each have an enlarged portion and a reduced diameter portion disposed distally of said enlarged portion, said enlarged portions being larger in diameter than the largest diameter of said set screws for permitting said blades to be inserted into or removed from said slots through transverse movement of said blades toward or away from said handle, respectively, said set screws being disposed in said reduced diameter portions of said keyways when said set screws are sufficiently loosened, said blades are seated against said base surfaces of said slots, and translated in a proximal direction, said reduced diameter portions being smaller in diameter than the largest diameter of said set screws for preventing transverse movement of said blades with respect to said slots when said set screws are tightened, thereby releasably locking said blades in said slots.   
     
     
       3. An instrument according to claim 2, wherein each of said slots includes a lip disposed on an upper edge of said slots for overhanging a portion of said blades when said blades are fully inserted and releasably locked in said slots. 
     
     
       4. An instrument according to claim 3, wherein said lips extend over the proximal end portions of said slots. 
     
     
       5. An instrument according to claim 4, and further including a transverse bore through said handle disposed proximally of said lips, said transverse bore intersecting said proximal end portions of said slots. 
     
     
       6. An instrument according to claim 3, wherein each of said slots includes a pair of lips disposed on the opposite sides of said slots, such that said lips extend over said shank portions of said blades when said blades are fully inserted and releasably locked in said slots. 
     
     
       7. An instrument according to claim 6, wherein said blades each have recesses disposed on opposite sides of said shank portions for registering with said lips when said enlarged portions of said keyways are in register with said set screws, for permitting transverse movement of said blades into or out of said slots past said lips. 
     
     
       8. An instrument according to claim 1, wherein said blades have working edges on their distal terminal ends which are dual-tapered. 
     
     
       9. An instrument for harvesting an iliac bone graft, comprising: an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, and a distal working portion including a pair of longitudinally extending, transversely spaced apart blade retaining slots; and   a pair of chisel-type blades adapted for being releasably, lockably housed in said slots, wherein said blades each have a main body portion and a shank portion, said shank portions each being adapted for placement in said slots and each having a keyway therein, and wherein said slots each have a longitudinally extending planar base surface and transversely extending, opposed side walls, and said base surfaces each include a transversely extending threaded bore for receiving one of a pair of set screws, said set screws being engageable with said keyways of said blades for locking said blades in said slots, wherein said blades have a tapered portion between said shank portion and said main body portion, and said side walls of said slots flare outwardly near the terminal end of said distal working portion for engagement against said tapered portions of said blades when said blades are fully inserted and releasably locked in said slots.   
     
     
       10. An instrument for inserting an iliac bone graft into a disc space, comprising: an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, a distal working portion including an enlarged abutment head on its terminal end, and a slide portion disposed between said proximal gripping portion and said distal working portion, said abutment head having a distal abutment surface for engaging an iliac bone graft; and   a bone graft retainer member having a main body slidably disposed on said slide portion of said handle and slidable between said abutment head and said proximal gripping portions, said retainer member including a pair of retaining fingers having proximal ends mounted on said main body of said retainer member and free distal ends, said distal ends of said retaining fingers extending distally beyond said abutment surface of said abutment head when said retaining member is in its distalmost position and including means for gripping a bone graft therebetween, said abutment head including a stop member disposed thereon proximally of, and at a predetermined distance from, said distal abutment face for engaging the anterior surfaces of vertebrae bounding said disc space and limiting the travel of said instrument into said disc space to substantially said predetermined distance.   
     
     
       11. An instrument according to claim 10, wherein said distal ends of said fingers are spring biased toward one another, and spaced apart from one another in an unloaded state a distance less than the height of a bone graft to be gripped. 
     
     
       12. An instrument according to claim 11, wherein said fingers comprise substantially flat spring steel members angled toward one another near their free distal ends. 
     
     
       13. An instrument according to claim 10, said main body of said retainer member having a bore in which said slide portion is received and a track in said bore for closely, slidably receiving a correlatively shaped part of said slide portion for substantially preventing transverse movement, while permitting free sliding movement, of said retainer member with respect to said slide portion. 
     
     
       14. An instrument according to claim 13, wherein said slide portion has a rectangular cross section, and said bore of said retainer member body is also rectangular, said track comprising a pair of grooves disposed in two opposite side walls of said bore for receiving the side walls of said rectangular shaped slide portion therewithin. 
     
     
       15. An instrument according to claim 14, wherein said proximal ends of said retaining fingers are mounted within said bore of said retainer member body, to the two opposite side walls adjacent to said walls having said grooves. 
     
     
       16. An instrument for inserting an iliac bone graft into a disc space, comprising: an elongate handle having a proximal gripping portion terminating in a substantially blunt striking surface, a distal working portion including an enlarged abutment head on its terminal end, and a slide portion disposed between said proximal gripping portion and said distal working portion, said abutment head having a distal abutment surface for engaging an iliac bone graft; and   a bone graft retainer member having a main body slidably disposed on said slide portion of said handle and slidable between said abutment head and said proximal gripping portions, said retainer member including a pair of retaining fingers having proximal ends mounted on said main body of said retainer member and free distal ends, said distal ends of said retaining fingers extending distally beyond said abutment surface of said abutment head when said retaining member is in its distalmost position and including means for gripping a bone graft therebetween, said slide portion having an upper surface and a lower surface and side surfaces therebetween, said abutment head having upper and lower surfaces substantially coplanar with said upper and lower surfaces of said slide portion and extension portions on each side which extend beyond the side surfaces of said slide portion, said extension portions having a pair of transversely extending stop lugs on their upper surface and a pair of transversely extending stop lugs on their lower surface for engaging the anterior surfaces of vertebrae bounding said disc space and limiting the travel of said instrument into said disc space.   
     
     
       17. An instrument according to claim 16, wherein said stop lugs are spaced proximally from said distal abutment surface of said abutment head a distance substantially equal to a desired offset of the anterior surface of such bone graft from the anterior extremity of such disc space when fully inserted therein. 
     
     
       18. An instrument according to claim 17, wherein said stop lugs on said upper surface and on said lower surface of said extension portions are spaced apart a distance greater than the width of said retaining fingers, said stop lugs, said retaining fingers, and said retainer member being substantially centered with respect to said abutment head and said slide portion such that said retaining fingers may pass freely between said stop lugs during sliding movement of said retainer member along said slide portion. 
     
     
       19. An instrument according to claim 13, wherein said body of said retainer member comprises a pair of substantially C-shaped halves attached together with said slide portion disposed therebetween. 
     
     
       20. A method of inserting an iliac bone graft into a disc space, comprising the steps of: gripping the bone grail between the distal ends of a retainer member, the retainer member being slidably disposed on a slide portion of the shaft of an insertion instrument;   engaging the central anterior surface of the bone graft with an engagement surface of an abutment head disposed on the distal end of such shaft;   placing the instrument with the gripped bone graft adjacent the anterior extremity of a disc space;   tapping on the proximal end of the shaft to drive it and the bone graft in a distal direction into the disc space, and simultaneously preventing entry of the retainer member into the disc space and sliding the retainer member proximally with respect to the slide portion of the shaft, thereby progressively removing the graft from the retaining fingers as the graft is driven into the disc space.   
     
     
       21. A method according to claim 20, further including the step of limiting the travel of the engagement surface of the abutment head into the disc space. 
     
     
       22. A method of harvesting an iliac bone graft, comprising the steps of: placing an extraction instrument comprising a proximal blunt striking surface and a distal working portion including a pair of parallel, transversely spaced apart chisel-type blades against the iliac ridge of the ilium of a patient;   tapping the proximal striking surface of the instrument to drive the parallel spaced apart blades into the ilium to a predetermined depth to create a pair of spaced apart parallel incisions in the ilium; and   removing the bone comprised between the parallel incisions from the ilium to form a rough bone graft for subsequent final reshaping.